Objective To examine the association of fetal alcohol exposure during pregnancy with child and adolescent behavioural development.

Design The Western Australian Pregnancy Cohort (Raine) Study recruited 2900 pregnancies (1989–91) and the 14-year follow up was conducted between 2003 and 2006.

Setting Tertiary obstetric hospital in Perth, Western Australia.

Population The women in the study provided data at 18 and 34 weeks of gestation on weekly alcohol intake: no drinking, occasional drinking (up to one standard drink per week), light drinking (2–6 standard drinks per week), moderate drinking (7–10 standard drinks per week), and heavy drinking (11 or more standard drinks per week).

Methods Longitudinal regression models were used to analyse the effect of prenatal alcohol exposure on Child Behaviour Checklist (CBCL) scores over 14 years, assessed by continuous z-scores and clinical cutoff points, after adjusting for confounders.

Main outcome measure Their children were followed up at ages 2, 5, 8, 10 and 14 years. The CBCL was used to measure child behaviour.

Results Light drinking and moderate drinking in the first 3 months of pregnancy were associated with child CBCL z-scores indicative of positive behaviour over 14 years after adjusting for maternal and sociodemographic characteristics. These changes in z-score indicated a clinically meaningful reduction in total, internalising and externalising behavioural problems across the 14 years of follow up.

Conclusions Our findings do not implicate light–moderate consumption of alcohol in pregnancy as a risk factor in the epidemiology of child behavioural problems.